Take the crab-meat out of the shell using a fork. Under the white meat will be the brown – while the white is light, delicate sweet, the brown is creamy, meaty and earthy.
Finely chop the shallots and the coriander and mix into the crab meat.
Using a peeler, peel the skin of the mango and shave ribbons of mango into the bowl.
Cut the cucumber in half and shave into ribbons too.
Make the dressing: add the oil, garlic, sugar, salt, lime and chilli flakes into a small bowl and mix together vigorously using a fork. It should be tart and sweet, with a real kick.
Add the dressing to the crab and mix – divide between two plates and serve.